Various arrangements of animal feeder are provided in which there is a trough into which feed can be deposited from a hopper above the trough. In most cases the feed material to be deposited can vary in particle size and viscosity so that it is often desirable to provide an arrangement which allows an adjustment of the opening through which the material can feed from the hopper into the trough.
In many cases the opening is provided by a simple shutter at the gap between the Hopper and the trough where the height of the shutter can be adjusted to vary the gap at the bottom of the shutter.
In U.S. Pat. No. 4,660,508 (Kleinsasser) issued Apr. 28, 1987 is disclosed a feeder which provides a shelf above the trough with the hopper discharging onto the shelf in a manner so that the feed remains on the shelf but can be moved from the shelf to the trough by the animal as required. Feeders of this type have achieved significant commercial success. Adjustment of the height of the shelf is necessary for the purpose of accommodating different types of feed and different feed rates and this is obtained by a hand crank screw which operates with a threaded nut to raise and lower a strap carrying the shelf. The screw is used in adjustment of this device because the deposit of the feed onto the self requires an accurate adjustment of the distance between the shelf and the bottom edge of the hopper so that cruder systems with a less fine adjustment have been rejected.
U.S. Pat. No. 5,603,285 also of Kleinsasser issued Feb. 18, 1997 discloses a further similar device where additional adjustment of the height of the shelf is possible but again fine adjustment is provided by a screw.
It is also known to provide arrangements in which adjustment in a relatively crude manner is effected by selecting one of a plurality of holes in which to locate the pin of an adjustment lever so that the adjustment is effected step by step. As the holes must be necessarily a certain distance apart, such an adjustment provides a relatively crude distance of adjustment so that the fine tuning necessary for determining the specific dimensions of an opening to accurately control the rate of flow of feed material is not possible in such a system. One example is shown in U.S. Pat. No. 6,637,368 (Bondarenko) issued Oct. 28, 2003. This provides a link which extends along one end wall of a feeder and a lever can be moved to place a pin into a selected one of a number of holes in the end wall.
In U.S. Pat. No. 6,923,142 issued Aug. 2, 2005 is disclosed and an arrangement in which a shelf is carried on straps which extend along the end walls of the hopper and are movable by an adjustment linkage defined by a plate carried on the end wall and a manually adjustable lever mounted for pivotal movement on the plate. The plate has an arcuate outer edge which is serrated to define an arcuate row of teeth and the lever is formed by a flat of sheet material which lies in a plane parallel to and slides over the plate and includes a portion thereof which is bent out of a plane of the lever into the plane of the plate which is also serrated with a row of teeth shaped to mesh with the teeth of the arcuate portion. The portion of the lever is movable in a direction away from the plate a non-meshing position in which the lever is free to move around the pivot axis.